This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Alzheimer's disease (AD) is a neurodegenerative disorder with a complex pathogenesis and for which there is limited therapeutic intervention. The major pathological hallmarks of AD are the accumulations of B-amyloid (AB) peptide, the hyperphosphorylation of tau, and neuronal damage. Accumulation of AB may be particularly important because mutations in specific genes, as occur in familial AD, are associated with increased AB levels. While these genetic mutations are responsible for the accumulation of AB in familial AD, the causative factors for increased levels of AB in most cases of AD are not known. Hypercholesterolemia and caffeine are two factors that are capable of modulating AB levels and may affect the pathogenesis of AD. Our longterm objectives are to identify risks and mechanisms by which these factors contribute to the pathology of AD. The objective of this proposal is to determine the extent to which and the mechanisms by which cholesterol-enriched diet triggers and caffeine attenuates or exacerbates AD-like pathology in rabbit brain. The hypotheses to be tested in this proposal are (1) that cholesterol-enriched diets cause B-amyloid (AB) accumulation, tau hyperphosphorylation and neurodegeneration involving modulation of adenosine A2A receptors (A2AR), inositol-1,4,5-trisphosphate receptors (IP3R), and ryanodine receptors (RyR), and (2) that caffeine-induced blockage of A2AR or blockade of calcium release through IP3R will attenuate and caffeine-induced release of calcium from RyR-regulated calcium channels will exacerbate AB accumulation, tau hyperphosphorylation and neurodegeneration. Our specific aims are as follows: Aim 1: Determine the extent to which the expression of A2AR, RyR and IP3R is altered in brain of rabbits fed a diet enriched in cholesterol;Aim 2: Determine the extent to which caffeine dose-dependently regulates cholesterol-induced AD-like pathology and modulates A2AR, RyR and IP3R in rabbit brain;and Aim 3: Determine the extent to which A2AR, RyR and IP3R are involved in cholesterol-induced AB accumulation, tau phosphorylation and oxidative damage. Successful completion of the work proposed here will increase our understanding of the cellular mechanisms by which two factors, cholesterol and caffeine, affect the pathogenesis of AD and may lead to newer and better therapeutics for the prevention or treatment of AD.